BAMAKO, Mali — In the face of fierce, all-night bombardment by the French military, Mali’s Islamist insurgents have hunkered down to fight again.

Barging into some of the mud-brick houses in the battle zone and ejecting residents, they have sought to implant themselves in the local population and add to the huge challenges facing the French military campaign to loosen their grip on Mali.

“They are in the town, almost everywhere in the town,” said Bekaye Diarra, who owns the pharmacy in Diabaly, which experienced French bombing well into the morning Tuesday but remained under the control of the insurgents. “They are installing themselves.”

Benco Ba, a parliamentary deputy there, described residents in fear of the conflict that had descended on them. “The jihadists are going right into people’s families,” he said. “They have completely occupied the town. They are dispersed. It’s fear.”

Just five days into the French military campaign, it was becoming clear that airstrikes alone will probably not be enough to root out these battle-hardened fighters, who know well the harsh grassland and desert terrain of Mali and have spent months accumulating arms, constructing defenses in their northern strongholds and reinforcing their ranks with children as young as 12 years old.

Containing their southern advance toward Bamako, the capital, is proving more challenging than anticipated, French military officials acknowledged Tuesday. And with the Malian Army in disarray and no outside African force yet assembled, displacing the rebels from the country altogether appears to be an elusive, long-term challenge.

The jihadists are “dug in” at Diabaly, Defense Minister Jean-Yves Le Drian of France said Tuesday at a news conference. From that strategic town, they “threaten the south,” he said, adding: “We face a well-armed and determined adversary.”

Le Drian also acknowledged that the Malian Army had not managed to retake the town of Konna, whose seizure by the rebels a week ago provoked the French intervention.

“We will continue the strikes to diminish their potential,” the minister said. Using advanced attack planes and sophisticated military helicopters, the French campaign has forced the Islamists from important northern towns like Gao and Douentza. But residents there say that while the insurgents suffered losses, many of them had simply gone into the nearby bush.

“Bombing will weaken them, and it will stop their advance,” said Djallil Lounnas, an expert on the region at the University of Montreal who has written widely on al-Qaida in the Islamic Maghreb, one of the main extremist groups in northern Mali. “But as soon as the bombing stops, they’ll come back.”

Since the French started bombing, he said, “the situation has changed slightly but not fundamentally.”

Other analysts said that while forcing the insurgents from the cities was achievable, eliminating them altogether would require considerable additional effort. “You can’t launch a war of extermination against a very tenacious and mobile adversary,” said Col. Michel Goya of the French Military Academy’s Strategic Research Institute. “We are in a classic counterinsurrectionary situation. They are well armed, but the weapons are not sophisticated. A couple of thousand men, very mobile.”

And they have been preparing for battle for months.

One resident of Gao who accompanied Islamist fighters to a desert hide-out in recent months described a vast system of underground caves big enough to drive cars into, said Corinne Dufka, a senior researcher at Human Rights Watch. Around 100 Islamist fighters, many of them bearded foreigners speaking Arabic, had gathered inside, stockpiling weapons, vehicles, generators and scores of barrels of gasoline, the resident said. The bunker was well camouflaged, almost invisible from the rugged roads, and had long been used by bandits in the area. But the Islamists were expanding the tunnels and, even before the French campaign, had been gathering in them from towns across the north.